1. Field of the Invention
The present invention pertains to tools and methods of using tools for eliminating air voids trapped underneath a membrane seam, and in particular to such tools and methods using rollers for contacting the membrane. The present invention offers particular advantages when used with roofing membranes.
2. Brief Description of the Prior Art
Flexible sheets or membranes are becoming increasingly popular in many areas of endeavor today. For example, single ply roofing systems cover a roof substrate with at least one layer of an elastomeric membrane. Air pockets are sometimes encountered when membranes are overlapped and joined with a liquid adhesive to form a continuous seam. Often, the strongest adhesive bond is created when the thickness of the adhesive layer underneath the membrane is carefully controlled, and air pockets trapped between the membranes can affect the thickness of the adhesive. Air pockets are also objectionable because they might totally displace adhesive from a given area of the membranes to be joined.
For these and other reasons, it is often desirable to eliminate air pockets, voids or gas bubbles from underneath a membrane. Air pockets are displaced from a given spot by being forced to travel underneath the membrane seam, under the application of a traveling pressure wave usually generated by a scraper blade or a pressure roller. However, in some applications, blades and rollers cannot be used effectively to remove air pockets in a practical commercial environment. For example, roofing systems sometimes employ relatively thick or heavy gauge moisture-impervious strips or sheets of elastomeric membrane material such as neoprene or polyvinyl chloride. Although roofing membranes are sometimes manufactured in widths up to 40 feet, large area roofs require several strips of the membrane material to be laid side-by-side so as to form a continuous covering extending across the entire surface area of the roof. In order to provide moisture-proof joints between adjacent sheets, the edges thereof are sometimes overlaid one on top of the other, and a liquid adhesive is applied between the overlapping portions. The seams formed in this manner are often quite long. Pushing a pressure roller along the length of the seams is frequently ineffective for removing air pockets since the air pockets are thereby made to travel great distances along the length of the seam and control thereover is frequently lost, with the air pockets, or a portion thereof remaining trapped under the membrane. Also, it is difficult to continuously control the pressure applied to the seam. As a result, concentrated effort is frequently required to address problem areas along the seam.
Given the presence of a membrane edge immediately adjacent the seam, it is desirable to force the air pockets in directions generally transverse to the seam, thereby minimizing the path length of travel underneath the membrane. However, using pressure rollers in multiple, relatively short strokes transverse to the seam is a tedious operation and is inefficient when air bubbles escape sideways from the pressure wave set up by the roller, traveling along the seam in a direction not intended. Accordingly a particular portion of the seam may have to be treated several times before most air bubbles are eliminated therefrom.